The network-based advertising systems and methods described herein are related generally to delivering advertising to users of the Internet. One type of prior advertisement delivery system looks for keywords in a user's search engine query, and displays advertisements to the user that are matched to the keywords identified. Thus, a search for “skis” may result in advertisements for skis being displayed. In addition, prior advertising systems index the textual content of websites and then display advertisements are associated with keywords that are included in the content of the website, when the website is visited by a user. In this manner, an advertisement for a sporting publication may be displayed upon a user accessing a sporting goods website.
However, these prior online advertising systems suffer from low click-through rates and low return on investment for advertisers because users are inundated with advertisements and do not perceive the ads to be of sufficient value to click on them. One source of this problem is that currently, advertisements delivered by search engines offer only a few lines of static text and a hyperlink. Low click-thru rates suggest that users frequently ignore such advertisements. Worse, users may perceive such advertisements in a negative manner, as “clutter” in the user's web browsing experience. This results in ineffective advertising for the advertiser and frustration for the user.